JP2000115016A - Full-duplex radio and its wraparound prevention method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely remove interference to a receiving signal due to the sneaking of a transmitting signal by providing a band stop filter by which a stop band is variably controlled and controlling the stop band in order to remove a reception frequency component in an operation from the transmitting signal. SOLUTION: The band stop filter 7 with a configuration where the stop band is variably controlled by a filter controller 8 is added at the output side of a band pass filter 2. A variable capacitance is arranged in a tuning circuit as the band stop filter 7, an applied voltage to the variable capacitance is variably controlled by a filter controller 8 to change the capacitance and the stop band is variably controlled. Thus, the reception frequency component is removed from the spectrum of the transmitting signal by the band stop filter 7 and, then, fed to transmission/reception sharing equipment 3. Therefore, the level of interference to the receiving signal which occurs by the sneaking of the component to a receiving part by the leakage of the transmission/reception sharing equipment 3 and the mismatching of an antenna is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-duplex radio and a method for preventing the sneak path.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing the configuration of a conventional transmitting / receiving section of a full-duplex radio capable of transmitting and receiving simultaneously.
The wireless transmission signal from the transmission unit 1 is sent to the antenna 4 via the duplexer 3 after unnecessary harmonic components are removed by the low-pass filter 2. The wireless reception signal received by the antenna 4 is input to the band-pass filter 5 via the duplexer 3, where a signal in a desired band is extracted and sent to the receiver 6. The control unit 10 controls operations of the transmission unit 1, the reception unit 6, and other circuits.

[0003]

FIG. 5 shows a frequency spectrum of a radio transmission signal on the output side of the low-pass filter 2, with a center frequency Tf (hereinafter referred to as a transmission frequency) Tf as a center. The level is attenuated as the distance from the frequency Tf increases, but the level that can be completely regarded as 0 is at a point farther away from the frequency Tf. And in general,
Center frequency of received signal (hereinafter referred to as reception frequency) Rf
Has a certain level. In FIG. 5, the reception frequency Rf is higher than the transmission frequency Tf.
The same is true for a low case. Accordingly, the components of the transmission signal near the reception frequency Rf are greatly attenuated due to the leakage from the port P1 to the port P2 of the duplexer 3 and the reflection due to the mismatch of the antenna 4, but as shown in FIG. Through the band-pass filter 5 having the following characteristics,
It becomes an interference wave for the received signal. Moreover, since the level of the received signal is much smaller than that of the transmitted signal, it is necessary to suppress this interference wave level. For this purpose, it is necessary to reduce the sneak of the transmission signal to the receiving unit due to the adjustment of the duplexer and the antenna circuit. However, this method has a limit, and another countermeasure has been required.

[0004] It is an object of the present invention to provide a full-duplex radio and a method of preventing the interference of the transmission signal, which can more reliably remove the interference with the reception signal due to the transmission signal.

[0005]

In order to achieve the above-mentioned object, the present invention provides a band rejection filter whose stop band can be variably controlled between an output of a transmitting unit and a duplexer. And controlling the stop band so as to remove the reception frequency component from the transmission signal.

Further, the present invention provides a transmitting means for generating a radio transmission signal, and feeds the radio transmission signal generated by the means to a duplexer after removing a reception frequency component contained in the signal. And a filter control means for controlling a stop band of the band stop filter on the basis of information on a reception frequency and a transmission frequency during operation. A full-duplex radio is provided.

[0007]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing a configuration example of a transmission / reception unit of a full-duplex radio equipped with a wraparound prevention method according to the present invention. The same circuits as those in the conventional configuration of FIG. 4 are denoted by the same reference numerals. . The difference is that a band rejection filter 7 having a configuration in which the rejection band can be variably controlled by a filter controller 8 is added to the output side of the band pass filter 2.

The band rejection filter 7 may be any filter that can variably control the rejection band. For example, a varicap is provided in the tuning circuit, and the voltage applied to the varicap is variably controlled by the filter controller 8. And the stopband is variably controlled. Alternatively, as another configuration method, a large number of taps are provided in the tuning coil, and a contact point is moved by a motor or the like controlled by the filter controller 8 to select which tap to connect, and the stop band is variably controlled. The reason why the rejection band of the band rejection filter 7 is made variable is that the transmission and reception frequencies assigned to the radio device change, so that it is necessary to match them.

FIG. 3 shows a transmission frequency Tf and a reception frequency Rf.
4 shows an example of the characteristics of the band rejection filter 7 when the signal is given. In order to control the characteristics of the band rejection filter 7 according to the transmission / reception frequency in this manner, the filter control 8
The transmission frequency T used at that time from the control unit 10
f and information indicating the reception frequency Rf are taken in. According to the value, the stop band of the band reject filter 7 is variably controlled so that the transmission signal component centered on the transmission frequency Tf is passed and the component centered on the reception frequency Rf is attenuated. As a result, as shown in the spectrum of the transmission signal (input to the duplexer 3) in FIG. 3, the power near the reception frequency Rf is greatly attenuated. Therefore, this component is generated due to the leakage of the duplexer 3 and the mismatch of the antenna.
As a result, the level of interference with the received signal caused by the wraparound can be greatly reduced.

In the configuration example shown in FIG. 1, the band rejection filter is provided on the output side of the low-pass filter.
Obviously, this may be the input side of a low-pass filter.

[0011]

According to the present invention, the reception frequency component is removed from the spectrum of the transmission signal by the band rejection filter and then fed to the duplexer, so that the interference caused by the sneaking into the reception unit can be greatly reduced. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a full-duplex wireless device according to the present invention.

FIG. 2 is a diagram illustrating an example of characteristics of a band rejection filter.

FIG. 3 is a diagram showing an example of a spectrum of a transmission signal on the output side of the band rejection filter 7 of FIG. 1;

FIG. 4 is a block diagram illustrating a configuration example of a conventional full-duplex wireless device.

FIG. 5 is a diagram illustrating an example of a transmission signal spectrum of a conventional full-duplex wireless device.

FIG. 6 is a diagram illustrating a characteristic example of a reception band-pass filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission part 2 Low-pass filter 3 Duplexer 7 Band rejection filter 8 Filter controller

Claims (2)

[Claims] 1. A band rejection filter whose rejection band is variably controllable is provided between an output of a transmitter and a duplexer, and the rejection band is controlled so as to remove a reception frequency component from a transmission signal during operation. A method for preventing sneaking of a full-duplex wireless device. 2. A transmission means for generating a radio transmission signal, and a radio transmission signal generated by the means for removing a reception frequency component contained in the signal and feeding the radio transmission signal to a duplexer. A band rejection filter whose stop band is variably controllable, and filter control means for controlling a stop band of the band rejection filter based on information on a reception frequency and a transmission frequency during operation. Full duplex radio to do.